JPS5813002B2 - Kanshitsusoshi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a humidity sensing element that is made of an oxide semiconductor and detects humidity as a change in electrical resistance.

As is well known, generally metal oxides (Fe304, Fe2
03, Al203, Cr203, etc.) have excellent water absorption properties and can be used as moisture sensing elements.

In other words, it takes advantage of the fact that the electrical resistance of a layer formed by depositing this type of metal oxide fine powder on the surface of an inorganic insulating substrate having a pair of opposing electrodes changes by a wide range in response to changes in humidity. It is something.

Moisture sensing elements using fine powder of the above metal oxides are physically
Although it is chemically and thermally stable, it generally has a high specific resistance, so even if there is a slight change in resistance due to moisture absorption and desorption phenomena, it is difficult to electrically detect this with high accuracy.

Therefore, several attempts have been made to lower the resistivity. For example, alkali metal oxides (Li20, K20,
0, Na20, etc.) have been added.

However, in this case, there are disadvantages that not only the humidity cycle history becomes significantly large, but also that reproducibility is poor and changes over time are large.

Accordingly, the present invention seeks to provide a moisture-sensitive element in which the above-mentioned drawbacks are eliminated.

The humidity sensing element of the present invention comprises a sintered body made of LiCoSb04 provided with at least one pair of electrodes, and a
CoSb045 mol% or more (excluding 100 mol%)
), a sintered body having a composition of Zn095 mol % or less (excluding 0 mol %) is a moisture sensing element provided with at least one pair of electrodes.

That is, the moisture sensing element of the present invention has LiCoSb04, which has a spine structure formed by sintering cobalt carbonate, lithium carbonate, and antimony oxide, as essential components, and if necessary, zinc oxide is mixed therein, press-molded, and sintered. The main body is what is obtained by doing so.

LiCoSb04 powder, which is an essential component in the present invention, contains, for example, L12CO3, COCO3 and Sb203 in 1
This can easily be obtained by weighing accurately to obtain a molar ratio of 2:1, mixing well with a little ball mill, pre-calcining at a temperature of about 700° C. for about 1 hour, and pulverizing.

The moisture-sensitive element of the present invention can be obtained by press-molding and firing the LiCoSbO+ powder alone or a mixture of LiCoSbO4 powder and ZnO powder as raw materials.

However, when adding and mixing the ZnO component, it is necessary to select a composition ratio of 95 mol % or less.

The reason for this is that if the composition ratio of ZnO is 95 molar or more, the range of change in resistance value with respect to humidity becomes small, making it unsuitable for practical use.

Next, the present invention will be explained by giving specific examples.

First, Li2CO3CoCO3 and Sb20 were precisely mixed in a molar ratio of 1:2:1 and mixed well using a ball mill.

Thereafter, this mixture was preliminarily calcined at 700C for 1 hour and then pulverized using a ball mill to obtain LiCoSb04 powder.

The thus obtained LiCoSb4 powder and ZnO powder were selected and mixed in a composition ratio (mold) as shown in the following table to prepare and prepare six types of raw materials.

Next, polyvinyl alcohol (caking) is applied to the above raw material powder.
was added and press-formed at a pressure of 1 ton/dm3, then 80
Heat and sinter at a temperature of 0 to 1300C for 2 hours to a thickness of rmm
Disk-shaped sintered bodies each having a diameter of 20 mr were obtained.

A pair of electrodes were provided on the main surface of this disc-shaped sintered body by baking a silver paste thereon, and lead wires were soldered to each to produce moisture-sensitive elements.

FIG. 1 is a plan view of the above-mentioned moisture-sensitive element, and 1 is Li.
CoSb04-based sintered body, 2, 2' are electrodes, 3, 3'
indicates a lead wire.

When the relationship between relative humidity and resistance value was determined for each of the humidity sensing elements obtained in the above manner, the results were as shown in FIG.

In FIG. 2, the numerical values of the symbols all correspond to the sample numbers, and the humidity-resistance relationship showed stable characteristics with no deviation due to humidity cycles.

For reference, FIG. 2 also shows a magnetite colloid type case as a conventional example.

Furthermore, each of these samples was left for 1000 hours at 40°C and 95% relative humidity to determine the change in characteristics (resistance value - humidity relationship) as shown in Figure 3 (for Examples 1 to 5). there were.

As is clear from the figure, LiCoSb04 according to the present invention
All of the moisture-sensitive elements in this system show almost no change in resistance and remain stable over time.

As described above, the humidity sensing element of the present invention always exhibits the required characteristics, there is no deviation due to humidity cycles, and the resistance change is large with respect to humidity changes, so it is possible to accurately measure humidity. Together with ease of manufacture and ease of handling, it can be said that it offers many advantages in practical use.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of the structure of a moisture-sensitive element according to the present invention;
FIG. 2 is a characteristic diagram showing the relationship between relative humidity and resistance value of the humidity sensing element according to the present invention, and FIG. 3 is a diagram showing the temporal characteristics of the humidity sensing element according to the present invention.

Claims (1)

[Claims] A moisture sensing element comprising a sintered body made of I LiCoSb04 and provided with at least one pair of electrodes. 2. A moisture-sensitive element comprising at least one pair of electrodes of a sintered body having a composition of LiCoSb045 molar proportion or more (however, excluding 100 molar proportions) and Zn095 molar proportion or less (however, excluding 0 molar proportions).